# Ethereum Address Key: `finance.crypto.ethereum_address` Ethereum wallet or contract address. 42 characters: 0x + 40 hex digits. May be EIP-55 checksummed (mixed case) or not. Page: Samples: `0x742d35Cc6634C0532925a3b844Bc3e7c1f2B9C2C`, `0x0000000000000000000000000000000000000000`, `0xd9965507d3b0ce0ce6932b0337db0c11b85fcf7d` ## Background ### Origin Ethereum was conceived in 2013 by programmer Vitalik Buterin.[[1]](https://en.wikipedia.org/wiki/Ethereum) The Ethereum network went live on 30 July 2015.[[1]](https://en.wikipedia.org/wiki/Ethereum) An Ethereum account's public address is made by taking the last 20 bytes of the Keccak-256 hash of the account's public key and adding 0x to the beginning.[[2]](https://ethereum.org/en/developers/docs/accounts/) An externally owned account's address is 42 characters long: a 20-byte segment written as 40 hexadecimal characters, plus the 0x prefix.[[2]](https://ethereum.org/en/developers/docs/accounts/) Contract accounts also have a 42-character hexadecimal address.[[2]](https://ethereum.org/en/developers/docs/accounts/) A contract deployed with the CREATE operation gets an address derived from the creator's address and the number of transactions sent from that address, known as the nonce.[[2]](https://ethereum.org/en/developers/docs/accounts/) A contract deployed with CREATE2 gets an address derived from the creator's address, a salt the creator picks and a hash of the contract's creation code.[[2]](https://ethereum.org/en/developers/docs/accounts/) The mixed-case form of the address is defined in ERC-55, Mixed-case checksum address encoding, created on 2016-01-14.[[3]](https://eips.ethereum.org/EIPS/eip-55) ERC-55 was written by Vitalik Buterin and Alex Van de Sande.[[3]](https://eips.ethereum.org/EIPS/eip-55) ERC-55 never changes the decimal digits 0 to 9, since they cannot be upper-cased.[[3]](https://eips.ethereum.org/EIPS/eip-55) ERC-55 keeps the address at 40 characters.[[3]](https://eips.ethereum.org/EIPS/eip-55) ERC-55 was designed to be backwards compatible with many hex parsers that accept mixed case, so that it could be introduced over time.[[3]](https://eips.ethereum.org/EIPS/eip-55) ERC-55 gives an average of 15 check bits per address, and puts the chance that a randomly mistyped address accidentally passes the check at 0.0247%.[[3]](https://eips.ethereum.org/EIPS/eip-55) ### Use The ethers library's getAddress function accepts non-checksum and checksum addresses and returns a normalized, checksummed address.[[4]](https://docs.ethers.org/v6/api/address/) When an address passed to ethers' getAddress contains both upper-case and lower-case letters, the function validates its checksum and throws an error if the checksum fails.[[4]](https://docs.ethers.org/v6/api/address/) The ethers documentation advises converting an address to lower case before passing it to getAddress if its checksum should be ignored.[[4]](https://docs.ethers.org/v6/api/address/) Treat a mixed-case address that fails its checksum as suspect, since it may carry a typo, rather than silently lower-casing it. (Meridian's view) Google's Blockchain Analytics documentation says addresses in its Ethereum dataset are indexed in all lowercase, and advises using LOWER() when working with mixed-case addresses.[[5]](https://docs.cloud.google.com/blockchain-analytics/docs/schema) Join and deduplicate on the lower-cased address, so that a checksummed copy and a lowercase copy of the same account match. (Meridian's view) ### Where you'll meet it Google's Blockchain Analytics lists Ethereum mainnet tables in BigQuery under bigquery-public-data.goog\_blockchain\_ethereum\_mainnet\_us.[[5]](https://docs.cloud.google.com/blockchain-analytics/docs/schema) Google's Ethereum dataset includes a transactions table, with materialized views clustered on its from\_address and to\_address columns.[[5]](https://docs.cloud.google.com/blockchain-analytics/docs/schema) ## Sources 1. [Ethereum - Wikipedia](https://en.wikipedia.org/wiki/Ethereum) — secondary source 2. [Ethereum accounts](https://ethereum.org/en/developers/docs/accounts/) — documentation 3. [ERC-55: Mixed-case checksum address encoding](https://eips.ethereum.org/EIPS/eip-55) — standard 4. [Documentation](https://docs.ethers.org/v6/api/address/) — documentation 5. [Dataset schemas \| Blockchain Analytics \| Google Cloud Documentation](https://docs.cloud.google.com/blockchain-analytics/docs/schema) — organisation